What is really happening when an aircraft surpasses the sound speed limit for us to hear and see a small ‘boom’?
In: Physics
So an airplane is constantly putting out sound. Sound moves at a specific speed, which for subsonic flight is faster than the plane itself is moving.
Let’s say a plane is in subsonic flight, starting at point 1. At point 1, one “piece” of sound leaves the engines and moves forward (at the speed of sound). The airplane moves to point 2, one yard further than point 1. In the time it took the plane to move 1 yard, the sound from point 1 has moved, say, 10 yards. That’s for regular flight.
Now let’s say a plane is flying at exactly the speed of sound. At point 1, the “piece” of sound leaves the engines and moves forward. The airplane moves to point 2 and emits another “piece” of sound, as it would in any situation. However, in this case the sound from point 1 reaches point 2 at the exact same time as the plane. So when the plane reaches point 2 and emits the second “piece” of sound, now you have 2 pieces of sound in the same spot (since the 1st one is moving right alongside the plane). Now you’ve doubled the intensity of the sound since you have twice the amount (the sound from point 1 and from point 2 are in the same place at the same time).
Now in real life sound isn’t being created once every yard, but rather continuously. So instead of 2 “pieces” of sound, you have a bunch all in the same place at the same time. So now you have a fast buildup of sound, and that added intensity is the sonic boom.
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